My tomato seedlings were started in late February in a germination kit with a grow light. About a little over a month ago, I transplanted them, but unfortunately most of my plants have a problem: there is a narrowed/contracted, hard woody area on the stem about 1-2cm above the soil line. They also had a few leaves just pop off in the week or two after transplantation. Are my seedlings going to survive? This issue seems to share characteristics of damping off, though the plants are a bit older and otherwise appear relatively healthy, other than some mild purpling on the underside of the leaves (perhaps a consequence of overwatering?).
The problem is consistent across 3 different varieties of tomato plant, yet my pepper and tomatillo varieties are all fine.
Advice greatly appreciated.